/Engine/Plugins/Runtime/SmartObjects/Source/SmartObjectsModule/Public/SmartObjectDefinition.h
validation filter class for preview.
[TSubclassOf](API\Runtime\CoreUObject\Templates\TSubclassOf)< [USmartObjectSlotValidationFilter](API\Plugins\SmartObjectsModule\USmartObjectSlotValidationFilter) > GetPreviewValidationFilterClass() const